Invited Speaker Series: A talk by Justin London at Goldsmiths, University of London.

There is no doubt that there are some songs that you just can’t help but dance to… but have you ever stopped to think that there is more going on than grooving to the beat?
There are several complex processes taking place as you figure out where the beat is, what it is and how fast it’s going. All this takes place before you begin to move your feet, nod your head or clap your hands.

The Carlton Dance

It Can Get Complicated!

In his presentation to the students on the MSc in Music, Mind and Brain at Goldsmiths, Justin London from Carleton College (USA) explained how our judgment of tempo is dependent on multiple factors both auditory and non-auditory. The auditory factors affecting our judgments include Beat Rate per Minute (BPM), Rate of surface activity, Dynamics and Spectral Flux.

Spectral Flux a measure of how the acoustical energy in various parts of the auditory spectrum varies over time. Music with low spectral flux will contain fewer events. while music with high spectral flux will necessarily have more events and can be more complex.

London spoke about a study which tested participants perceived tempo judgments on music with High Flux and Low Flux at different tempos (London et al., 2015). Each test of tempo was played to the participant both quietly and loudly, to also assess the effect of volume on tempo perception. The study revealed that music with High Flux was perceived as being faster than the simple Low Flux music.

Figure 1. Justin London’s results bar graph for Flux test.

Step to The Beat!

London and his colleagues (2016) conducted a study to examine if the perception of musical tempo can be affected by the visual information provided. They started by recording videos of participants dancing to songs that are known to have high ‘grooviness’, where ‘groove’ was described as the degree to which a listener will want to move along with the beat of a song (Think Motown, Stevie Wonder).

The dancers were required to dance along to songs with their tempo increased or decreased by 5% (time- stretched versions), as well as in the song’s original tempo (baseline tempi versions). For the time-stretched versions, participants were asked to dance freely, whereas for the baseline tempi versions, participants were requested to dance either in a relaxed (slow) or vigorous (fast) manner.

Motion capture animations based on the video recordings of the dance movements were then presented to a different group of participants to rate the speed of the songs. The second group of participants were exposed to the music in 3 different ways: audio-only, audio with video, and video-only.

Figure 2. An example of how participants were exposed in the audio with video condition (from London et al., 2016)

The results of the study found that the relaxed versions of the song were perceived as slower, and vigorous versions as faster. There seems to be a visual-auditory tempo illusion, which means that the differing movement (relaxed / vigorous) of the dancers can influence one’s perceived tempo, even when their body movements and the beat of music are in synchrony (London et al., 2016).

Results also showed that the songs with relaxed versions were perceived as even slower when compared to the songs with highest tempo (130BPM) when presented without audio (video only). This was explained that it is acceptable to have slow movements in a fast song, but not fast movements in a slow song. (Imagine rocking your heart out to the song Starry Starry Night (Vincent)!) Thus, London and his colleagues concluded that when one encounters a conflicting connection between the audio and visual input, this information would be further integrated in a meaningful manner – in a way that makes the “best sense” to the perceiver.

Watch What You’re Listening To!

The McGurk Effect (McGurk & Macdonald, 1976) is an fascinating example of cross modal perception. It demonstrates the powerful link between sight and hearing. A great example of the McGurk Effect has been demonstrated using a video loop of a person pronouncing a syllable like “ga” twice. The video and audio tracks are purposefully played out of sync to begin with and gradually synchronize. The confusion experienced was initially created and then resolved by vocal motor neurons. Recent research has discovered the existence of

mirror neurons. These are the same neurons which make you laugh or cringe when you see someone fall over Charlie Chaplin style Manfredi, Adorni and Proverbio, (2014).

Mirror neurons are multimodal association neurons that increase their activity during the execution of certain actions and whilst hearing or seeing corresponding actions being performed by others (Schreuder, 2014). There is marked increase their activity during the execution of certain actions and whilst hearing or seeing corresponding actions being performed by others.

When it comes to perceiving musical tempo, during a live performance, these neurons play an important role in “feeling” the beat. Imagine seeing a marimba player or Taiko drummer perform. As you watch their hand elevate and strike there is a point where what you see will affect what hear. Schutz and Lipscomb, (2007) found that the gesture of a percussionist can affect the observers visual perception of the tempo of the performance. Observing a drummer perform an epic solo whilst attending to the rhythm of the numerous beats he or she plays generally leads to jaw dropping observation. The flux and volume, as mentioned before, will also affect how you perceive a performance and react. Not to mention the adrenaline rush most people feel when they see their favorite band performing.

Click on the link below to experience the confounding Mcgurk effect; “magic of the mind” for yourself.

Truly, we can see that there are many sensory modalities involved in such a simple task like keeping up with the rhythm of a song. So the next time when you’re in concert watching your favorite performer singing and moving along with the song, remember that seeing them is (almost?) having as big an impact as hearing them.

This blog was written following Justin London’s presentation to Goldsmiths’ Music, Mind and Brain MSc students on 1/12/ 2016 as part of the ‘Invited Speaker’ series.